Alcoholysis of vegetable oils and animal fats has been investigated extensively for producing fatty acid alkyl esters, which can be used as diesel fuels. Commonly used catalysts for alcoholysis include alkali hydroxides and alcoholates. These non-enzymatic catalysts are disadvantageous as they have to be removed with glycerol, a by-product, and cannot be reused. Further, purification of glycerol is difficult as it contains a large amount of such a catalyst.
As an alternative, lipases, enzymatic catalysts, have been used for preparing alkyl esters from natural oils in an enzymatic alcoholysis reaction. However, they may be inactivated by certain alcohols used in or by glycerol produced from the alcoholysis reaction. Replacing or regenerating the lipases increases the costs. Thus, there exists a need to develop a cost-effective method of manufacturing alkyl esters on a commercially applicable scale, in which inactivation of lipases is minimized.